The value of ∫(x→1, a)[x] f '(x)dx, a > where [x] denotes the greatest integer not exceeding x is
(a) a f(a) – {f(1) + f(2) + ... + f([a])}
(b) [a] f(a) – {f(1) + f(2) + ... + f([a])}
(c) [a] f([a]) – {f(1) + f(2) + ... + f(a)}
(d) a f([a]) – {f(1) + f(2) + ... + f(a)}.
